Flying to London next year? British Airways will no longer be the only choice for a non-stop flight to and from Seattle starting June 1 when Northwest Airlines starts daily service next between Seattle-Tacoma International and London Heathrow airports.

Minneapolis-based Northwest today became the third carrier this year to announce new service between Seattle and Europe when it said it plans to begin non-stop service into Heathrow from Seattle, Detroit and Minneapolis next year.

The news will bring the total number of daily European nonstops to and from Sea-Tac to six: British Airways to London, Northwest Airlines to Amsterdam, SAS to Copenhagen, Air France to Paris, and starting next spring, Lufthansa to Frankfurt.

Northwest's announcement raises the stakes for British Airways which currently has the only daily non-stop between Seattle and London. Whether the new competition will translate into lower fares remains to be seen.

"Logically, it would drive prices down," says Joe Brancatelli, publisher of an online newsletter for business travelers called joesentme.com. "But whether than means, on a mile-per-mile basis, Seattle fares will drop, is an open question. It still might be cheaper to fly, say, Seattle-New York then New York-London for a lower absolute price."

Either way, he points out "Seattle will win because there will be more nonstop options than ever to Europe. ''

That's welcome news, especially for London-bound travelers who have become annoyed with British Airway's rising fuel surcharges and service problems, including lost luggage and flight delays in and out of Heathrow. A class-action suit filed in Seattle earlier this year alleges that the airline has lost 550,000 bags this year — some of them permanently.

Airline industry watchers say U.S. and foreign carriers are jockeying for position in anticipation of competition heating up when a European "Open Skies" agreement takes effect next March. That pact will allow more U.S. carriers to use Heathrow, British Airways' base, and allow Europe-based airlines to fly to more U.S. cities.

"It's all about 'Open Skies' with the European Community, which will mean lots more flights from lots more places as airlines are free to fly wherever they want," says Brancatelli.

Air France, for instance, could add a Seattle-London route, or Lufthansa could decide to fly between Seattle and Paris.

Bloggers weighing in on a discussion board at www.airliners.net speculate that Northwest's announcement is aimed at heading off competition from British-based Virgin Atlantic Airways which has stated that Seattle is on the shortlist of new routes when it takes delivery of new Boeing 787s.

Northwest will operate the new London flights with its joint venture partner, KLM Royal Dutch Airlines. The Seattle flight, on an Airbus A330 plane, will leave at 10:05 p.m. (10:55 p.m. on Fridays) and arrive the next day at 4:15 p.m. (5:05 p.m. on Fridays). The return flight will leave London at 6:30 p.m. and arrive at 8:55 p.m. in Seattle on the same day.

The airline said it will continue its daily round-trip flights between Detroit and London Gatwick Airport.